Montana Natural Heritage Program

Community Field Guide

Scientific Name:
Abies lasiocarpa / Arnica cordifolia Forest

Common Name:
Subalpine fir / heartleaf arnica Forest

Community Description

Summary:
This major type is particularly expansive on calcareous substrates in the drier mountain ranges east of the Continental Divide. It is common on well-drained benchlands and north-facing slopes in mountainous terrain, although it is found on all aspects and degrees of slope. This type commonly occurs on calcareous substrates with similar adjacent topography but noncalcareous sites supporting Abies lasiocarpa / Vaccinium scoparium. Soils are slightly acidic, mostly nongravelly loams to silty clay loams derived from a broad range of parent materials, including limestones, granitics, shale, quartzite and andesite. The observed elevation range is 7,300 to 9,500 feet, but the actual range is no doubt broader.

Warmer, drier sites often support Abies lasiocarpa / Calamagrostis rubescens, Abies lasiocarpa / Clematis columbiana, or Festuca idahoensis and Artemisia tridentata ssp. vaseyana dominated mountain parks. It is distributed on sites drier than those supporting Abies lasiocarpa / Thalictrum occidentale and occurring at generally higher elevations, usually transitional to the moister/colder Abies lasiocarpa / Vaccinium scoparium forest.

Environment:
This is a major type in the drier mountain ranges east of the Continental Divide, being particularly expansive on calcareous substrates. It is common on well-drained benchlands and north-facing slopes in mountainous terrain, although it is found on all aspects and degrees of slope. A common pattern is for this type to occur on calcareous substrates with similar adjacent topography but noncalcareous sites supporting Abies lasiocarpa / Vaccinium scoparium. Soils are slightly acidic, mostly nongravelly loams to silty clay loams derived from a broad range of parent materials, including limestones, granitics, shale, quartzite and andesite. The observed elevation range is 7,300 to 9,500 feet, but the actual range is no doubt broader.

Warmer, drier sites often support Abies lasiocarpa / Calamagrostis rubescens, Abies lasiocarpa / Clematis columbiana, or Festuca idahoensis and Artemisia tridentata ssp. vaseyana dominated mountain parks. It is distributed on sites drier than those supporting Abies lasiocarpa / Thalictrum occidentale and occurring at generally higher elevations, usually transitional to the moister/colder Abies lasiocarpa / Vaccinium scoparium forest.

Vegetation:
An overstory of Abies lasiocarpa dominates late seral stands. Undergrowth is generally depauperate, depending on degree of canopy closure; even young stands may have less than 5% total cover. Arnica cordifolia is the diagnostic forb; other common forbs are Astragalus miser, Pyrola secunda, Aster conspicuus, and Osmorhiza chilensis or Osmorhiza depauperata. Pinus albicaulis is scattered to abundant in the highest elevation examples of this type.

Range:
This is a major, predominantly large patch and matrix community type found in the drier mountain ranges of Montana primarily east of the Continental Divide and ranging into northwestern Wyoming and extreme eastern Idaho.

Dynamics:
Abies lasiocarpa and Picea engelmannii are generally slow to reestablish following disturbance. Waist high 50-year-old Abies specimens are not unusual. This habitat type is generally dominated by an open to dense tree canopy of seral species including Pseudotsuga menziesii, Pinus contorta and Picea engelmannii with a subcanopy or sapling layer of Abies lasiocarpa and Picea engelmannii extensive data and reconnaissance observations indicate Pinus contorta and Pseudotsuga menziesii and all admixtures dominate seral stages and persist to near climax conditions. In early seral stands, Shepherdia canadensis, Juniperus communis or Symphoricarpos oreophilus are often well represented but decline (with the occasional exception of Shepherdia canadensis) to scattered individuals as the tree canopy closes.

Global Rank: G5 State Rank: S5

Community References

Identifier:
CEGL000298

Author:
01-03-10 / S. V. Cooper, MTNHP

Citations:
Hoffman and Alexander 1976, Loope 1969, Pfister et al. 1977, Reed 1969, Steele et al. 1981, Steele et al. 1983, Youngblood and Mueggler 1981

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This information is from the:
Montana Natural Heritage Program
Montana State Library--Natural Resource Information System
1515 East Sixth Ave., Helena, MT 59620-1800 406 444-3989
mtnhp.org
mtnhp@mt.gov